Container processing lines are commonly found in various fields of manufacture which involve containerizing liquid goods for sale. A very common form of container processing line is that of the distillery industry, where glass containers, such as bottles are filled with liquor, capped at a capping station, conveyed to a labelling station where appropriate labels are applied to each bottle and then conveyed to a packing station where the labelled bottles are placed in a carton for shipping. A concern in operating such a line is that the capping station, labelling station and packaging station may all be operating at different speeds. This can result in backlogs of containers upstream of the various stations thus necessitating some form of arrangement for accumulating containers as one machine attempts to catch up with the other machine.
Thus, significant advances have been made in the field of accumulation tables which may be made up of a plurality of conveyors spaced alongside one another having gathering rails which cause an accumulation of containers to expand laterally onto new conveyors, as they wait to be processed by the next station. However, with such accumulation tables and particularly with glass containers, there is a considerable amount of shock to the bottles as they slam into one another on the accumulation tables. Attempts have, therefore, been made to control the formation of a backlog of containers upstream of each station.
U.S. Pat. Nos. 3,607,547 and 3,738,891 are directed to this problem. In U.S. Pat. No. 3,607,547, it suggests the use of a single sensor upstream of a labeller and a single sensor downstream of the labeller in the container processing line to alter the speed of the labeller in an essentially "on/off" approach. In sensing a predetermined backlog of containers upstream of the labeller, the labeller is accelerated to a faster labelling speed to attempt to clear the backlog and once removed, resumes a slower speed. Similarly when a backlog of containers is sensed downstream of the labeller, the machine is slowed down.
It was realized, as explained in U.S. Pat. No. 3,738,891 that the use of a single sensor upstream and another downstream of the labeller caused frequent speed changes. Thus, the approach in this latter United States patent is to provide a plurality of sensors upstream of the labeller which function to vary the speed of the labeller in an "on/off" approach in response to the various sensors indicating certain backlogs of containers to thus run the machine at different speeds depending upon the backlog in attempting to control the backlog of containers upstream of the machine and maintain some degree of consistent flow of containers therethrough. However with this approach and the provision of several sensors, large accumulation tables are required upstream of the machine and since the system operates on the basis of "on/off," there is no control over maintaining a desired backlog of containers upstream of the machine which would enable a continued operation of the capping machine or the packing machine, should the labeller stop or should one of the other machines stop.
The control system, according to this invention, overcomes a number of the above problems by providing an efficient control on the labeller speed dependent upon the condition of backlog of containers upstream and downstream of the labeller while maintaining a desired backlog upstream of the labeller to provide a more overall efficient container processing line with regard to keeping the various units running while the speeds of the various units may fluctuate.